TUPAIID OSTEOLOGY AND RELATIONSHIPS 249 



though many of the similarities may have developed under the stimulus 

 of similar arboreal habits, yet there is a real genetic relationship between 

 the two groups. 



Ptilocercus is somewhat more lemur-like than Tupaia in its skull and 

 dentition. The malar and jaw are stouter; the tendency toward dipro- 

 todonty more pronounced; the molars more bunodont, with incipient 

 hypocone-cingula. I was, however, surprised to find that in its post- 

 cranial skeleton Ptilocercus is on the whole less lemur-like than Tupaia. 

 It has fourteen dorsals and five lumbars, 6 its ribs are broad and flat, the 

 thorax and sternum are shorter, the dorsal vertebrae have low spines, and 

 the parapophyses of the lumbars are but feebly developed. The limbs 

 are less elongate, the ilium rodlike rather than spatulate, the pubis and 

 ischium small, and the pubic symphysis very short; whereas it is long 

 in Tupaia, Macroscelidae, and Lemurs. The scapula is broader than in 

 Tupaia, the humerus less elongate, the supinator crest more pronounced, 

 the entocondyle and entepicondylar foramen are prominent, and the 

 capitellum globular. The hallux and pollex seem to be capable of 

 marked divergence. All this appears to indicate that Ptilocercus is less 

 agile and squirrel-like, perhaps more Marmosa-like, in habits than 

 Tupaia; also that many of the lemurine characters of Tupaia may have 

 been developed independently. 



ENTOMOLESTES AN EOCENE TUPAIID 



One of the American Museum Expeditions to the Bridger Basin se- 

 cured there a minute lower jaw, which was described by Matthew 7 in 

 1909 and named by him Entomolestes grangeri in honor of its discoverer. 

 Doctor Matthew noted the resemblance of this jaw to that of Tupaia, 

 but owing to lack of adequate material for comparison, he left the genus 

 incertse sedis as to family, merely referring it to the lnsectivora. The 

 subsequent acquisition by the museum of skeletons representing the 

 principal types of recent Insectivores has led me to compare this precious 

 relic with the jaws of recent and fossil Insectivores, Bats, and Primates 

 of many families. This comparison has brought into clear view the close 

 agreement in essentials of Entomolestes with the Tupaiidas, especially 

 the small Tupaia modesla; so that I feel reasonably safe in stating thai 

 in the Bridger Eocene of North America there lived a very primitive 

 representative of the Oriental Tupaiidse. 



From certain indications I infer that there was a small first incisor: 



•The complete vertebral formula of Ptiloceroui is: C7, 1)14, L5, Cd. :?.'?. 

 7 The Carnivora and lnsectivora of the Bridger Basin, Middle EDocene. Mem. Auier, 

 Mus. Nat. Hist., vol. 9, part 6, 1909. 



